1. Field of the Invention
The present invention relates to establishing a contention window, and more particularly, to an apparatus and a method for establishing a contention window in a WiMedia wireless network able to reduce data transmission latency time and maximize data transmission efficiency by establishing an optimal contention window for each access category (AC) on the basis of the number of devices and access categories (AC) acquired from a beacon which has been received during a beacon period (BP), in a prioritized contention access (PCA) method of a WiMedia wireless network.
2. Description of the Related Art
In general, a beacon group is a wireless local network configured to have only WiMedia devices without a coordinator controlling the devices. All of the devices in the network need to transmit beacons during a beacon period (BP) and other devices also need to transmit the beacons. Through these beacons, the WiMedia devices may detect all devices adjacent thereto and be synchronized with the adjacent devices.
Meanwhile, the transmitting and receiving of data between devices in WiMedia network is performed by a distributed reservation protocol (DRP) method and a prioritized contention access (PCA) method.
The DRP method is a non-contention method in which, when a data transmitting device requests a reservation, a data receiving device determines request permission on the basis of its own state and a reservation state within the beacon group.
In contrast, the PCA method is a contention method in which a media acquiring device that transmits data through the contentions of devices during a transmission opportunity (TXOP) period. Since the PCA method is the contention method, the contentions of the devices included in the beacon group rapidly concentrated at a starting point of the PCA period. In this case, in the PCA method according to the related art, a back-off process is performed by random contention windows from the minimum window (CWmin) to the maximum window (CWmax). As a result, a predetermined bandwidth may not be efficiently used.